#include <stdio.h>

#define USE_EPOLL 1
//#define EPOLL_SUPPORT

int main()
{
#if USE_EPOLL 
// 如果EPOLL_SUPPORT未定义，则编译不通过
#ifndef EPOLL_SUPPORT
#error "epoll need xxx support"
#endif

	// do something...
#endif
    return 0;
}